Preparation of ultrathin ReS2 nanosheets and their application to Q-switched Er-doped fiber lasers

We study the exfoliation of ultrathin ReS2 nanosheets from the prepared ReS2 powder and their application to Q-switched Er-doped fiber laser.XRD,Raman,and XPS spectra confirm the successful preparation of the layered ReS2.SEM images show that the obtained ReS2 sheets have lateral size below 200 nm.The thickness of the ReS2 nanosheets is smaller than 5 nm according to the AFM results.ReS2/PVA film is applied as a saturable absorber in an Er-doped Q-switched fiber laser,and a minimum pulse duration of 2.4μs and an output power of 1.25 mW are obtained,indicating the potential application to Q-switched lasers.

Vertically standing PtSe_2 film: a saturable absorber for a passively mode-locked Nd:LuVO_4 laser

The novel vertically standing Pt Se2 film on transparent quartz was prepared by selenization of platinum film deposited by the magnetron sputtering method, and an Nd:Lu VO4 passively mode-locked solid-state laser was realized by using the fabricated Pt Se2 film as a saturable absorber. The X-ray diffraction pattern and Raman spectrum of the film indicate its good crystallinity with a layered structure. The thickness of Pt Se2 film is measured to be 24 nm according to the cross-section height profile of the atomic force microscope image. Highresolution transmission electron microscopy images clearly demonstrate its vertically standing structure with an interlayer distance of 0.54 nm along the c-axis direction. The modulation depth(ΔT) and saturation fluence(Φs)of Pt Se2 film are measured to be 12.6% and 17.1 μJ∕cm2, respectively. The obtained mode-locked laser spectrum has a central wavelength of 1066.573 nm, with a 3 d B bandwidth of 0.106 nm. The transform limited pulse width of the mode-locked laser was calculated to be 15.8 ps. A maximum average output power of 180 m W with a working repetition rate of 61.3 MHz is obtained. To the best of our knowledge, this is the first report of the generation of ultrafast mode-locked laser pulses by using layered Pt Se2 as a saturable absorber.

Enhancing upconversion of Nd3+ through Yb^(3+)-mediated energy cycling towards temperature sensing

Photon upconversion of lanthanides has been a powerful means to convert low-energy photons into high-energy ones.However,in contrast to the mostly investigated lanthanide ions,it has remained a challenge for the efficient upconversion of Nd^(3+)due to the deleterious concentration quenching effect.Here we report an efficient strategy to enhance the upconversion of Nd^(3+)through the Yb^(3+)-mediated energy cycling in a core-shell-shell nanostructure.Both Nd^(3+)and Yb^(3+)are confined in the interlayer,and the presence of Yb^(3+)in the Nd-sublattice provides a more matched energy for the upconversion transitions occurring at the intermediate state of Nd^(3+)towards much better population at its emissive levels.Moreover,this design also minimizes the possible cross-relaxation processes at both intermediate level and the emissive levels of Nd^(3+)which are the primary factors limiting the upconversion performance for the Nd^(3+)-doped materials.Such energy cycling-enhanced upconversion shows promise in temperature sensing.